JP3744775B2 - Paper separation method using floatation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a paper separation / sorting method using a floatation / sink method, recycled paper regenerated from paper separated by this method, and a paper separating apparatus.
[0002]
[Prior art and problems to be solved by the invention]
In Japan, about 31 million tons of paper was produced in 1997. Of this mass-produced paper, about 90% of “paperboard” used in corrugated cardboard is reused as used paper, whereas general “paper” such as printing paper and wrapping paper. Is less than 30%.
On the other hand, the production of recycled paper is increasing today as part of the recycling of used paper (Japan Paper Federation "Used Paper for Utilization of Its Valuable Resources" March 1998). In order to manufacture this recycled paper, it is necessary to sort the paper in advance. However, since the present situation greatly depends on the sorting state at the time of used paper collection, there arises a problem that foreign substances other than different types of paper and contraindicated products are mixed. In addition, in recent years, an effective paper sorting method has been required to promote recycling, and new research on physical paper sorting has become necessary (CA Hardie et. Al .; CIM Bull, Vol 92, No. 1031, p.131-137 (1999), G. Wouch; Am Ink Maker, Vol 74, No. 7, p.44, 46, 50 (1996)). Under such circumstances, it has become an urgent task to develop a new sorting / separating technique for separating paper (particularly newspaper and advertising paper) by type.
[0003]
[Means for Solving the Problems]
The present invention provides a method of sorting and separating at least two types of paper, in particular newspapers and advertising papers, which are the most common among papers, by the floatation method. In the separating means of the present invention, a piece of paper such as newspaper and advertisement paper, which may be cut (for example, cutting with a shredder or the like), is put into a container together with a solvent (water). To this solvent (water) is added a dispersant such as sodium lignin sulfonate and optionally a reagent for neutralizing the surface potential of the paper such as sulfate such as aluminum sulfate. Thereafter, when the container itself is allowed to stand, a piece of paper (for example, newspaper) that floats on the liquid surface and a piece of paper (for example, advertising paper) that settles on the bottom separate and float.
[0004]
The subject of the present invention is at least two types of papers having a specific gravity of 0.2 or more, wherein the specific gravity of the at least one type of paper is not less than the specific gravity of the solvent, and the specific gravity of any other paper is A method of separating a paper having a specific gravity of less than the specific gravity of the at least one paper or less than the specific gravity of the solvent and the specific gravity of any paper other than the paper being equal to or higher than the specific gravity of the solvent. It is a method comprising a step of standing paper in a solution containing a dispersant. It is preferable that the dispersant is at least one selected from the group consisting of sodium lignin sulfonate, water glass, gelatin and starch, and the concentration of the dispersant in the solution is 10 to 100 mg / liter. The solution may further contain a sulfate. The sulfate is at least one selected from the group consisting of aluminum sulfate, ferrous sulfate and ammonium alum, and the concentration of the sulfate in the solution is preferably 5 mg / liter or more. The at least two types of paper may be newspaper and advertising paper.
[0005]
Another subject of the present invention is recycled paper recycled from the paper separated by the method described above. Still another subject matter of the present invention contains 10 to 100 mg / liter of at least one selected from the group consisting of sodium lignin sulfonate, water glass, gelatin and starch, and further contains aluminum sulfate, ferrous sulfate and ammonium alum. An apparatus for paper separation comprising a container containing a solution containing 5 mg / liter or more of at least one selected from the group consisting of:
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The flotation method is the same as the separation method, which is also called the sedimentation method, and is a method of collecting the floating product and the subsidence product as separate products. That is, it is a method in which suspended matter is floated and settled by a chemical physical action in a solution to which a reagent or the like is added. The floatation method of the present invention is characterized in that the sedimentation method itself is applied to paper sorting, and not only the sedimentation product (for example, advertising paper) that settles, but also the floating product (for example, newspaper) that floats is collected. It is. Further, as a feature of the sedimentation method of the present invention, stirring is only necessary at the time of addition of the drug, it is not necessary during the separation, it can be separated at natural atmospheric temperature, and some drug is necessary but inexpensive. Another characteristic is that tap water can be used as a solvent.
[0007]
The paper to be separated in the present invention is at least two kinds of papers having different specific gravity of 0.2 or more, preferably 0.35 or more. That is, the specific gravity of at least one of these papers only needs to be more than these values from the specific gravity of any paper other than this (or these) papers. Further, the specific gravity of the at least one paper is not less than the specific gravity of the solvent (1 in the case of water), and the specific gravity of any paper other than this paper is less than the specific gravity of the solvent, or at least one of these The specific gravity of the paper must be less than the specific gravity of the solvent, and the specific gravity of any paper other than this paper must be greater than or equal to the specific gravity of the solvent. In particular, when the solvent is water, the specific gravity of the at least one paper is preferably 1 or more, particularly 1.05 or more, and the specific gravity of the other paper is preferably less than 1, particularly less than 0.75.
Specifically, the method of the present invention separates a group of newspapers, ordinary printing paper (printer paper, recycled paper) and the like from a group of advertising paper, various glossy magazines, pamphlets and the like. It is particularly suitable for separating and sorting newspaper and advertising paper. The paper to be separated according to the present invention is preferably cut to some extent to make a piece. For example, it is not impossible to float and separate newspaper or the like in a general size, but it is not appropriate from the viewpoint of performing separation because it takes a long time to become familiar with the solvent (water). Separation can be performed more effectively if the float-sink separation is performed with a certain size. According to the results of Examples described later, it is considered that a strip of about 2 × 16 mm after shredder cutting, in which the size is uniform, is suitable for the floatation method.
[0008]
The solvent used for separation in the present invention is preferably water, particularly tap water, at low cost. It is also possible to manipulate the specific gravity of the solution by performing a treatment such as adding an oil / surfactant.
The paper separating solution of the present invention contains a dispersant.
As this dispersant, a dispersant used for flotation is suitable, and examples thereof include electrolytes such as sodium silicate and sodium phosphate, sodium lignin sulfonate, water glass, gelatin and starch, and lignin sulfonic acid. Sodium, water glass, gelatin and starch are preferred, and sodium lignin sulfonate is more preferred.
The paper separation solution of the present invention contains at least one selected from these dispersants, but the concentration is affected by factors such as the degree of paper cutting. When the paper is cut into small pieces, it is considered that the necessary amount of the dispersant is somewhat increased as the specific surface area is increased. Considering these, the concentration of the dispersant is preferably 10 to 100 mg / liter, more preferably 20 to 80 mg / liter, and further preferably 25 to 60 mg / liter.
[0009]
The paper separating solution of the present invention may further contain a sulfate.
Since the surface of paper is porous and hydrophilic and the surface potential in the solvent (water) shows a negative value, this sulfate neutralizes this surface potential, thereby promoting the separation of the paper. I think that. As the sulfate, aluminum sulfate, ferrous sulfate and ammonium alum are preferable, and aluminum sulfate is particularly preferable.
The paper separation solution of the present invention contains at least one selected from these sulfates, but the concentration is affected by factors such as the degree of paper cutting as described above. Considering these, the concentration of sulfate is preferably 5 mg / liter or more, more preferably 5 to 50 mg / liter, and further preferably 5 to 20 mg / liter.
[0010]
The order in which these reagents are added to the solvent (water) is not particularly limited, but the necessary reagents are first dissolved in the solvent (water), and after the solution is thoroughly blended, paper is added and a stir bar, etc. The method of stirring lightly is preferable. Although the standing time depends on the size and amount of paper to be separated, it is usually enough to stand for about 5 to 10 minutes after the stirring.
[0011]
In the paper separated and selected in the present invention, the floating product and the subsidence product are generally collected separately. Thereafter, the recovered paper is subjected to dehydration of both papers if necessary in the use or process of the paper. In the normal regeneration process, there is a process in which an aqueous solution such as alkaline water is added in the next step to loosen the paper in a boiled shape, so it is considered that there is no particular problem even if some moisture is contained. After that, the process of removing heavy foreign matter (clips, etc.) from the loosened paper, the process of separating into fiber and foreign matter and garbage, the deinking process (by adding chemicals such as surfactant to the loosened paper and blowing in air The ink floats together with the foam, while the hydrophilic paper fiber sinks and separates from the ink.), Dust removal process (using centrifugal force to remove fine dust and sand with large specific gravity, and again Two-stage dust removal that removes debris using a screen is often used.), Dehydration process, bleaching process (after removing ink and removing dust, using hydrogen peroxide solution, etc. to further increase whiteness) And bleaching.), Washing process (cleaning is performed in order to finally remove dust in each of the above processes), and the like, and then reused as recycled paper.
[0012]
【Example】
In this embodiment, in order to deal with these problems, basic research was conducted to sort newspapers and advertising papers that are highly common among papers using the floating sorting method and the floating and sinking method. The effect of dispersant concentration on the floatability of newspaper and advertising paper was investigated by the floatation method, and the effect of drug concentration and pH on the floatability of newspaper and advertising paper was examined by the floatation method for comparison.
In this example, general newspaper and advertising paper were used, and both papers were arbitrarily cut with scissors (Examples 1 to 4, Comparative Example 1) and shredded (cutting machine) into pieces (Example 5). ) Was used as a sample. As for the size of the paper after cutting, the paper piece cut with scissors is 3 to 11 mm long × 7 to 35 mm wide, and the paper piece after shredding is almost uniform and 2 mm long × 16 mm wide. The specific gravity of newspaper and advertising paper was 0.71 and 1.09, respectively. Further, as a result of X-ray analysis of newspaper and advertising paper, the newspaper contained Al ₂ O ₃ and SiO ₂ , and Al was present at about 2.36% and Si was present at about 2.89%. On the other hand, the advertisement paper contained CaO and MgO, and Ca was present at about 32.00% and Mg was present at about 1.74%.
[0013]
Example 1 (single floating)
Newspaper and advertisement paper cut with scissors were each placed in a 100 ml beaker with 5 g each and stirred. Next, after adding sodium lignin sulfonate (Ligninesulfonic Acid Sodium Salt, addition concentration 0 to 50 mg / liter, hereinafter referred to as LGS) as a dispersant, floatation and sedimentation was performed. The resulting levitated matter and sediment were dried and then weighed to determine the respective levitating rates for newspaper and advertising paper. In this example, no pH adjusting reagent or the like was added, and the reaction was carried out under conditions of natural pH (about pH 7).
FIG. 1 shows the results when the newspapers and the advertising papers are individually floated and sunk. The floating rate (marked with ●) of newspaper increased as the LGS concentration increased, and reached 100% when the LGS concentration was 12 mg / liter or more. On the other hand, the floating rate (■ mark) of the advertising paper was 30% to 50% regardless of the LGS concentration.
[0014]
Example 2 (single floating)
The surface of paper such as newspaper is porous and hydrophilic, and the surface potential in water shows a negative value. In this embodiment, since the process is performed near the natural pH of pH 7, it is necessary to neutralize this surface potential. Then, the electrical neutralization of the paper near neutrality was examined using aluminum sulfate. That is, since aluminum sulfate becomes aluminum hydroxide that exhibits a positive zeta potential in the vicinity of neutrality, it is considered that the aluminum sulfate is adsorbed between the fibers of the newspaper and the newspaper is electrically neutralized. As a result, newspapers are expected to be hydrophobic and easily float without floating in the water. Therefore, when aluminum sulfate was added, the influence of the LGS concentration on the floating rate of newspaper and advertising paper was examined.
In this example, the relationship between the LGS concentration and the flying height when aluminum sulfate was further added to the same aqueous solution as in Example 1 at 10 mg / liter was examined. The result is shown in FIG. The floating rate of newspaper showed 100% at all concentrations regardless of the amount of LGS added, and the floating rate of advertising paper was 10% at the maximum. In addition, when the LGS concentration was 25 mg / liter or more, the floating rate of the advertising paper was 0%, and all the paper pieces were settled.
[0015]
From the results of Examples 1 and 2, it was found that newspapers and advertising papers can be selected by the floatation method. In particular, by adding aluminum sulfate, the floating rates of newspaper and advertising paper were 100% and 0%, respectively. This is presumably because the surface potential of the newspaper was neutralized by aluminum hydroxide, and the newspaper surface, which originally had hydrophilic properties, became hydrophobic because it was hydrophobic. Furthermore, it is speculated that the newspaper and the advertisement paper are dispersed by the dispersion action of the LGS, and a clear floating phenomenon occurs due to the difference in specific gravity between them (newspaper 0.71 and advertisement paper 1.09). From these facts, it was shown that news paper and advertising paper can be separated and selected by the floating and sinking method of the present invention.
[0016]
Example 3 (mixed float and sink, influence of dispersant concentration)
Next, referring to the results of Examples 1 and 2, a floating / sinking experiment was performed using a sample in which newspaper and advertising paper were mixed.
FIG. 3 shows the relationship between the LGS concentration and the floating rate when newsprint and advertising paper are mixed. In this example, 10 mg / liter of aluminum sulfate was added, and the amount of LGS added was varied in the range of 5 to 50 mg / liter. When the concentration of LGS used as a paper dispersant is 12 mg / liter or less, there is no significant difference in the floating rate, but when the LGS concentration is 25 mg / liter, the difference in the floating rate between the two is the largest. became. At this time, the rising rate of newspaper (● mark) was 97%, and that of advertising paper (■ mark) was 0%. As described above, this is considered to be the concentration at which the electrical neutralization of aluminum hydroxide with aluminum sulfate and the effect of the dispersant LGS are most effectively generated. On the other hand, when the concentration of LGS was further increased, it was confirmed that newspapers tend to settle without rising. This is presumably because the newspaper became hydrophilic due to the excessive dispersant and settled because it contained too much moisture.
[0017]
Example 4 (mixed floatation, influence of sulfate concentration)
Next, in FIG. 3, the LGS concentration at which the difference in the levitation rate was maximized was made constant at 25 mg / liter, and the concentration of aluminum sulfate was changed in the range of 0 to 50 mg / liter in the same manner as in Example 3 to perform the levitation experiment. Went. FIG. 4 shows the relationship between the concentration of aluminum sulfate and the floating rate of newspaper and advertising paper. When the aluminum sulfate concentration was 10 mg / liter, the floating rates of newspaper (● mark) and advertising paper (■ mark) were 97% and 0%, respectively, and the effect of floating and sinking appeared clearly. When the density is higher than that, the rising rate of the newspaper decreases and becomes a constant value around 60%. On the other hand, it can be confirmed that the floating rate slightly increases in the advertisement paper. From the above results, it was found that the newspaper paper and the advertising paper can be most effectively selected by the floatation / sink method under the conditions of aluminum sulfate concentration of 10 mg / liter and LGS concentration of 25 mg / liter.
[0018]
Example 5 (mixing up and down, selection of paper cut with a shredder)
Finally, FIG. 5 shows the rise and fall results of a mixing experiment of newspaper and advertising paper, which was performed in the same manner as in Example 3 except that the paper was shredded with a shredder. In this example, in consideration of the result of Example 3, 10 mg / liter of aluminum sulfate was added. In this figure, the same result as in FIG. 2 of Example 2 was obtained, but when the LGS concentration was 50 mg / liter, the floating rate of newspaper was 97% and the floating rate of advertising paper was 0%. This is presumably because the paper piece treated with the shredder is more uniformly stripped than the piece arbitrarily cut with scissors, so that the specific surface area is large and the newspaper is easy to absorb the pulp solution. As a result, in order to disperse the shredded newspaper, it was necessary to slightly increase the amount of LGS added compared to the result of Example 3. In other words, it was found that the amount of dispersant added to separate newspaper and advertising paper should be increased as the paper piece to be sorted becomes smaller.
[0019]
Comparative Example 1 (Floating sorting method using a flotation machine)
The experimental procedure was to mix 5 g each of newspaper and advertising paper as a sample, put them in 500 ml of pure water, and stirred for 5 minutes. Thereafter, dodecyl ammonium acetate (Laurylamine Acetate, addition concentration 0 to 50 mg / liter, hereinafter referred to as DAA) was added as a collection agent. After further stirring for 3 minutes, several drops (about 8 mg) of methyl isobutyl ketone was added as a foaming agent, and a floating selection experiment using a flotation machine was performed. At this time, the impeller rotational speed is constant at 2300 rpm. After the flotation was completed, the obtained suspended matter and sediment were dried and weighed to determine the floating rate of newspaper and advertising paper. In addition, the effect of pH was also examined in this floating sorting method. That is, flotation was performed with the DAA collector concentration fixed and the pH adjusted to 3-11. The floating rate was similarly calculated | required about the obtained floating substance and sediment.
[0020]
FIG. 6 shows the results of a flotation experiment in which newspaper and advertising paper are mixed and the concentration of the collection agent DAA is changed under the conditions of a pulp concentration of 1%, a flotation time of 3 minutes, and a pH of 5. The horizontal axis indicates the DAA concentration, the vertical axis indicates the flying height (0 to 100%), the newspaper is indicated by ● and the advertising paper is indicated by ■. The rising rates of newspaper and advertising paper both show low values of approximately 10% or less regardless of the DAA concentration. Although this was observed during the experiment, it was thought that the main cause was that many of the pieces of paper entangled with the impeller for stirring of the flotation machine without floating, and lost the floating property. Further, FIG. 7 shows the relationship of the floating rate (0 to 10%) when the DAA concentration is kept constant at 20 mg / liter. From FIG. 7, the influence of pH on the floating rate of newspaper and advertising paper was not confirmed, and both showed low floating rates of 8% or less, as in the results shown in FIG. From the above, it can be said that it is difficult to sort newspapers and advertising papers by the usual floating sorting method.
[0021]
【The invention's effect】
As a result of the basic sorting experiment of newspaper and advertising paper using the floating sorting method and the floating and sinking method, the following was found.
(1) In the floating sorting method using a flotation machine, a piece of paper entangled with the impeller and the sorting effect was low. On the other hand, it became clear that newspapers and advertising papers were well sorted by the floatation method without agitation.
(2) In the float / sink method, it was necessary to neutralize the surface potential of the piece of paper and to appropriately aggregate or disperse it. Also, the amount of dispersant added for separation increased as the paper piece became smaller.
(3) In this floating and sinking experiment, it is clear that separation and sorting of newspaper and advertising paper can be performed almost 100% when the sodium lignin sulfonate concentration is 25 mg / liter or 50 mg / liter and the aluminum sulfate concentration is 10 mg / liter. Became.
[0022]
According to the method of the present invention, it was found that the newspaper has a floating rate of 97% (the rate at which a piece of paper floats on the liquid surface) and the advertising paper has a floating rate of 0%, so that the newspaper and the advertising paper can be separated almost completely. In addition, it became clear that the amount of dispersant added for separation increased as the piece of paper became smaller, and as with aluminum sulfate, it became clear that there was an appropriate amount added depending on the size of the piece of paper. From the above, it can be recognized that this floatation method is sufficiently effective for paper sorting.
Further, even after a large amount of recovered paper (newspaper and advertising paper) is simultaneously applied to a cutting machine (shredder), it is considered that sorting and separation for each paper type becomes possible. In particular, it is useful for the reuse of waste paper that needs to be sorted and separated in advance as represented by recycled paper.
[Brief description of the drawings]
FIG. 1 is a diagram showing the floating ratio of each paper with respect to the concentration of LGS when LGS is used as a dispersant and newspaper paper and advertising paper are separately separated and sorted by a floating method. No sulfate was used, and the pH was 7.
FIG. 2 is a diagram showing the floating rate of each paper with respect to the concentration of LGS when newspaper paper and advertising paper are separately separated and sorted by floating and sinking methods using LGS and aluminum sulfate. The concentration of aluminum sulfate was 10 mg / liter and the pH was 7.
FIG. 3 is a diagram showing the floating rate of each paper with respect to the concentration of LGS when newsprint and advertising paper are mixed and separated by floatation using LGS and aluminum sulfate. The concentration of aluminum sulfate was 10 mg / liter and the pH was 7.
FIG. 4 is a diagram showing the floating rate of each paper with respect to the concentration of aluminum sulfate when newsprint and advertising paper are mixed and separated by floatation using LGS and aluminum sulfate. The concentration of LGS was 25 mg / liter and the pH was 7.
FIG. 5 is a diagram showing the floating ratio of each paper with respect to the concentration of LGS when newspaper paper and advertising paper mixed with shredder using LGS and aluminum sulfate are shredded and separated and sorted. The concentration of aluminum sulfate was 10 mg / liter and the pH was 7.
FIG. 6 is a diagram showing the floating ratio of each paper with respect to the concentration of DAA when news paper and advertising paper are mixed and separated and sorted by the floating sorting method using DAA. The pulp density was 1%, the floating time was 3 minutes, the pH was 5, and stirring was performed.
FIG. 7 is a diagram showing the floating rate of each paper with respect to pH when news paper and advertising paper are mixed and separated and sorted by the floating sorting method using DAA. The concentration of DAA was 20 mg / liter, and stirring was performed.

Claims (5)

The specific gravity of at least two types of papers differing by 0.2 or more, wherein the specific gravity of the at least one type of paper is greater than or equal to the specific gravity of the solvent, and the specific gravity of any other paper is less than the specific gravity of the solvent, Or a method of separating paper in which the specific gravity of the at least one type of paper is less than the specific gravity of the solvent and the specific gravity of any other paper is equal to or higher than the specific gravity of the solvent, and the paper contains a dispersant. Ri consists step of standing in solution, the a dispersing agent sodium lignosulfonate, wherein the solution further aluminum sulphate, at least one sulfate salt selected from the group consisting of ferrous and ammonium alum sulfate Including methods.   The method according to claim 1, wherein the concentration of the dispersant in the solution is 10 to 100 mg / liter, and the concentration of the sulfate in the solution is 5 mg / liter or more.   The method according to claim 1 or 2, wherein the at least two types of paper are newspaper and advertising paper. The manufacturing method of the recycled paper containing the method as described in any one of Claims 1-3. Lignin sulfonic acid sodium containing 10-100 mg / l, further aluminum sulphate, at least one sulfate salt selected from ferrous and the group consisting of ammonium alum from a container comprising a solution containing more than 5mg / l sulfuric acid A device for paper separation.

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